Field of the Invention
The present invention relates to a method and apparatus for assembling a direct injector unit to a cylinder head.
Related Art
In a direct injection engine mounted on a vehicle such as an automobile in which fuel is directly injected into a combustion chamber, injectors of a direct injector unit are assembled to a cylinder head by pressing the injectors into a plurality of injector mounting holes formed in the cylinder head. The direct injector unit includes multiple injectors whose number is the same as or larger than that of cylinders, and a fuel pipe to which the multiple injectors are fixed. The fuel-inlet-side end portion of each injector is fit into a connection portion formed around the fuel pipe, whereby the corresponding injector is connected to the fuel pipe. Therefore, depending on a fitting condition of the injectors and the fuel pipe, a variation may be generated in a posture of a leading end portion of each injector. Also, due to a manufacturing error of the injector mounting holes of the cylinder head or the like, when the injectors are inserted into the injector mounting holes of the cylinder head, the leading end portions of the injectors may come into contact with the injector mounting holes, resulting in damages to the injector mounting holes or the injectors.
In order to cope with this problem, there has been disclosed an assembly method and guide tools in which guide tools 103 screwed into screw holes 102 of a cylinder head 101 are inserted into through-holes 105 of a delivery pipe (fuel pipe) 104 as shown in FIG. 5 such that postures of injectors 106 are corrected by being guided by the guide tool 103, whereby an assembly of an injector unit 107 is performed while worker's burden is reduced (see JP-A-2010-019132, for example).
Also, according to a known a fuel injection valve assembly and its manufacturing method as shown in FIG. 6, a fuel injection valve assembly 116 is configured by mounting collar members 111, stopper members 112, and a plurality of fuel injection valves 113 on a single rail member 115 in advance, and then a cylinder head of an engine is assembled with the fuel injection valve assembly 116 (see JP-A-2003-239828, for example).
However, according to the methods of JP-A-2010-019132 and JP-A-2003-239828, it is necessary to mount the guide tools 103 for assembly, or the collar members 111 and the stopper members 112 in advance. Thus, a man-hour for mounting or a man-hour for demounting increases, resulting in a reduction in productivity. Also, in a site having a large production volume or a large number of models, a quantity or number of tools or the number of kinds of tools that should be prepared increases, and a return mechanism for returning a used tool or jig to a mounting process is necessary. Further, since a tool, a jig, or the like is mounted to the cylinder head or the injectors to finally become a product, damages may be caused by contact, generated chips may bite into the product, or screw holes used once to mount a jig may be reused for fastening, resulting in a reduction in product quality. Furthermore, assurance quality may be reduced due to a reduction in a function or accuracy attributable to jig wear, or variation in assembling accuracy may be caused by differences in jig handing abilities among workers. Therefore, it is difficult to keep product quality constant.